High Number Of False-positive Results Research Articles

Antibody Cross-Reactivity in Serodiagnosis of Lyme Disease.

Lyme disease is a tick-borne disease caused by spirochetes belonging to the Borrelia burgdorferi sensu lato complex. The disease is characterized by a varied course; therefore, the basis for diagnosis is laboratory methods. Currently, a two-tiered serological test is recommended, using an ELISA as a screening test and a Western blot as a confirmatory test. This approach was introduced due to the relatively high number of false-positive results obtained when using an ELISA alone. However, even this approach has not entirely solved the problem of false-positive results caused by cross-reactive antibodies. Many highly immunogenic B. burgdorferi s.l. proteins are recognized nonspecifically by antibodies directed against other pathogens. This also applies to antigens, such as OspC, BmpA, VlsE, and FlaB, i.e., those commonly used in serodiagnostic assays. Cross-reactions can be caused by both bacterial (relapsing fever Borrelia, Treponema pallidum) and viral (Epstein-Baar virus, Cytomegalovirus) infections. Additionally, a rheumatoid factor has also been shown to nonspecifically recognize B. burgdorferi s.l. proteins, resulting in false-positive results. Therefore, it is necessary to carefully interpret the results of serodiagnostic tests so as to avoid overdiagnosis of Lyme disease, which causes unnecessary implementations of strong antibiotic therapies and delays in the correct diagnosis.

Transcranial versus direct electrical stimulation for intraoperative motor-evoked potential monitoring: Prognostic value comparison in asleep brain tumor surgery.

ObjectiveSafe resection of gliomas involving motor pathways in asleep-anesthesia requires the combination of brain mapping, to identify and spare essential motor sites, and continuous monitoring of motor-evoked potentials (MEPs), to detect possible vascular damage to the corticospinal tract (CST). MEP monitoring, according to intraoperative neurophysiology societies, is generally recommended by transcranial electrodes (TES), and no clear indications of direct cortical stimulation (DCS) or the preferential use of one of the two techniques based on the clinical context is available. The main aim of the study was to identify the best technique(s) based on different clinical conditions, evaluating the efficacy and prognostic value of both methodologies.MethodsA retrospective series of patients with tumors involving the motor pathways who underwent surgical resection with the aid of brain mapping and combined MEP monitoring via TES and DCS was evaluated. Irreversible MEP amplitude reduction (>50% compared to baseline) was used as an intraoperative warning and correlated to the postoperative motor outcome. Selectivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were computed for both techniques.ResultsFour hundred sixty-two patients were retrospectively analyzed, and only 1.9% showed a long-term motor impairment. Both TES and DCS obtained high specificity and NPV for the acute and 1-month motor deficit. Sensitivity was rather low for the acute deficit but excellent considering the 1-month follow-up for both techniques. DCS was extremely reliable in predicting a postoperative motor decline (PPV of 100% and 90% for acute and long-term deficit, respectively). Conversely, TES produced a high number of false-positive results, especially for long-term deficits (65, 87.8% of all warnings) therefore obtaining poor PPV values (18% and 12% for acute and 1-month deficits, respectively). TES false-positive results were significantly associated with parietal tumors and lateral patient positioning.ConclusionsData support the use of mapping and combined monitoring via TES and DCS. The sole TES monitoring is reliable in most procedures but not in parietal tumors or those requiring lateral positioning. Although no indications are available in international guidelines, DCS should be recommended, particularly for cases approached by a lateral position.

To Evaluate the Efficacy of Tissue Autofluorescence (Velscope) in the Visualization of Oral Premalignant and Malignant Lesions among High-Risk Population Aged 18 Years and Above in Haroli Block of Una, Himachal Pradesh.

ABSTRACTIntroduction:Visually enhanced lesion scope (Velscope) that identifies reduction in tissue fluorescence in dysplasia can prove to be effective in screening for potentially malignant lesions. The objective of the present study was to evaluate the effectiveness of device that utilizes the principles of tissue autofluorescence (Velscope) in the detection of dysplastic and/or neoplastic changes in oral mucosal lesions using biopsy and histopathology as “gold standard.”Materials and Methods:Out of nine hundred fifty patients with suspicious oral mucosal lesions, 250 patients were subjected to conventional oral examination followed by Velscope examination. The autofluorescence characteristics of 250 patients were compared with the results of histopathology. Biopsies were obtained from all suspicious areas identified on examination. The sensitivity, specificity, positive and negative predictive values were calculated for Velscope examination.Results:The Velscope examination showed sensitivity and specificity values of 75.00% (95% CI: 69.63%-80.37%) and 61.39% (95% CI: 55.35%–67.42%) respectively while the positive and negative predictive values were 31.58% (95% CI: 25.82%-37.34%) and 91.18% (95% CI: 87.66%-94.69%) respectively.Conclusion:The definite diagnosis of the presence of dysplastic tissue changes in the oral lesions cannot be made alone with the Velscopic examination. The high number of false-positive results limits its efficiency as an adjunct despite its reasonable sensitivity. However, It can serve to alleviate patient anxiety regarding suspicious mucosal lesions in a general practice setting due to high negative predictive value. Also, a combined approach of Velscope examination and conventional oral examination may prove to be an effective diagnostic tool for early detection of malignant oral mucosal lesions.

The diagnostic accuracy and clinical impact of FDG-PET/CT follow-up for patients on adjuvant immunotherapy for high-risk malignant melanoma.

The benefit of FDG-PET/CT in follow-up of patients treated with adjuvant immunotherapy after resection of high-risk malignant melanoma (MM) is debated. This study evaluated the diagnostic accuracy and clinical impact of FDG-PET/CT for diagnosing MM recurrence during the first year after surgery. We retrospectively included 124 patients with resected high-risk MM, who received adjuvant immunotherapy and follow-up FDG-PET/CT. Clinical information and AJCC-8 stage was obtained from patients' medical records. Recurrence was verified by biopsy/progression on a subsequent scan leading to change of treatment. Non-recurrence was assumed when no metastases were observed until the subsequent follow-up scan. Incidence of recurrence, sensitivity, specificity, positive and negative predictive values (PPV and NPV) were outcome measures. Incidence rate of MM recurrence was 0.27 [95% CI 0.17-0.37] per person-year during the first-year. Recurrence was detected in 13 patients (10%) at 3-month FDG-PET/CT, in 10 patients (8.1%) at 6months, 1 patient (0.8%) at 9months, 3 patients (2.4%) at 12months. The overall sensitivity, specificity, PPV, and NPV were 97% [86-99], 82% [78-86], 39% [29-50], and 99% [98-99], respectively. The PPV trended towards higher values as disease stage increased. At the 3-month scan, the majority of actions derived from positive findings were surgery or earlier expedition of the subsequent follow-up scan. The high rate of recurrence in patientswith high-risk MM treated with adjuvant immunotherapy emphasizes the need for follow-up. The potential harm by a moderately low specificity reflecting a high number of false-positive results must be weighed against the benefit of early detection of recurrence.

Evaluation of Three Commercial Interferon-γ Assays in a Bovine Tuberculosis Free Population.

The interferon-γ assay has been used worldwide as an ancillary test for the diagnosis of bovine tuberculosis (bTB). This study aimed to describe, based on the bTB-free status in Switzerland, the difference of applying a more stringent cutoff point of 0.05 compared with 0.1 for bTB surveillance. Moreover, the effect of time between blood collection and stimulation, culture results, optical density values, and the influence of testing different breeds were evaluated. Blood samples from a total of 118 healthy cows older than 6 months were tested with three commercial interferon-gamma assays. To confirm the bTB-free status of the tested animals and to investigate potential cross-reactions with nontuberculous mycobacteria, pulmonary and abdominal lymph nodes in addition to ileal mucosa from each cattle were used for the detection of viable Mycobacteria spp. by specific culture. Significant differences regarding the proportion of false-positive results between the two Bovigam tests and between Bovigam 2G and ID Screen were found. Samples analyzed with Bovigam 2G were 2.5 [95% confidence interval (CI) 1.6–3.9] times more likely to yield a false-positive test result than samples analyzed with Bovigam TB. Similarly, the odds ratio (OR) for testing samples false-positive with ID Screen compared with Bovigam TB was 1.9 (95% CI 1.21–2.9). The OR for testing false-positive with ID Screen compared with Bovigam 2G was less to equally likely with an OR of 0.75 (95% CI 0.5–1.1). When using a cutoff of 0.05 instead of 0.1, the OR for a false-positive test result was 2.2 (95% CI 1.6–3.1). Samples tested after 6 h compared with a delayed stimulation time of 22–24 h were more likely to yield a false-positive test result with an OR of 3.9 (95% CI 2.7–5.6). In conclusion, applying a more stringent cutoff of 0.05 with the Bovigam 2G kit generates a questionable high number of false-positive results of one of three tested animals. Furthermore, specific breeds might show an increased risk to result false-positive in the Bovigam 2G and the ID Screen assays.

Ethical Challenges With Smartwatch-Based Screening for Atrial Fibrillation: Putting Users at Risk for Marketing Purposes?

Background: Atrial fibrillation is the most common persistent arrhythmia. It is associated with increased mortality and morbidity such as stroke. The early detection of atrial fibrillation can significantly reduce the risk of stroke through preventive anticoagulation. Smartwatches offer the opportunity to screen for atrial fibrillation in the general population. This paper aims to analyze the ethical challenges associated with screening for atrial fibrillation using smartwatches.Methods: This is an ethical analysis. The methodology is based on the principle-orientated approach of Beauchamp and Childress. The principles of beneficence, non-maleficence, justice, and autonomy have to be guaranteed given the influence of private companies, privacy protection, liability and doctor-patient-relationship. The work is based on a systematic literature research.Results: There is currently no evidence that screening for atrial fibrillation with smartwatches improves the outcome and reduces the number of adverse events. The high number of false-positive results can lead to harm. The principle of non-maleficence is violated. The over-reliance on and the lack of adequate education by smartwatches can worsen the doctor-patient relationship. However, the relationship can also be improved by the proactive participation of the patient, which leads to greater autonomy, compliance and in the end beneficence. Since smartwatches are consumer goods, there is a risk for greater disparities in the poor and rich population. There is also a risk of discrimination against ethnic minorities due to underrepresentation in training data and study cohorts. The principle of justice is violated. The storage of sensitive medical data by private companies also raises many ethical and legal concerns.Conclusion: This analysis has shown that the use of smartwatches to detect atrial fibrillation is currently in an ethical perspective problematic. The lack of evidence and the high number of false-positive results can lead to harm. As smartwatches provide only little information about the possible consequences, informed consent cannot be assumed. Ethical implementation could be archived if doctors provide smartwatches to patients who have been shown to benefit from them. The implementation and education should be managed by the doctor.

Application of Six Detection Methods for Analysis of Paralytic Shellfish Toxins in Shellfish from Four Regions within Latin America.

With the move away from use of mouse bioassay (MBA) to test bivalve mollusc shellfish for paralytic shellfish poisoning (PSP) toxins, countries around the world are having to adopt non-animal-based alternatives that fulfil ethical and legal requirements. Various assays have been developed which have been subjected to single-laboratory and multi-laboratory validation studies, gaining acceptance as official methods of analysis and approval for use in some countries as official control testing methods. The majority of validation studies conducted to date do not, however, incorporate shellfish species sourced from Latin America. Consequently, this study sought to investigate the performance of five alternative PSP testing methods together with the MBA, comparing the PSP toxin data generated both qualitatively and quantitatively. The methods included a receptor binding assay (RBA), two liquid chromatography with fluorescence detection (LC-FLD) methods including both pre-column and post-column oxidation, liquid chromatography with tandem mass spectrometry (LC-MS/MS) and a commercial lateral flow assay (LFA) from Scotia. A total of three hundred and forty-nine shellfish samples from Argentina, Mexico, Chile and Uruguay were assessed. For the majority of samples, qualitative results compared well between methods. Good statistical correlations were demonstrated between the majority of quantitative results, with a notably excellent correlation between the current EU reference method using pre-column oxidation LC-FLD and LC-MS/MS. The LFA showed great potential for qualitative determination of PSP toxins, although the findings of high numbers of false-positive results and two false negatives highlighted that some caution is still needed when interpreting results. This study demonstrated that effective replacement methods are available for countries that no longer wish to use the MBA, but highlighted the importance of comparing toxin data from the replacement method using local shellfish species of concern before implementing new methods in official control testing programs.

Impact of visual inspection and radiographs for caries detection in children through a 2-year randomized clinical trial: The Caries Detection in Children–1 study

BackgroundVisual inspection (VIS) with radiographic examination (RAD) is the recommended diagnostic strategy for detecting caries in children; however, this recommendation is based on accuracy studies. The authors conducted a clinical trial to compare the detection and subsequent treatment of carious lesions in primary molars performed with VIS alone and with RAD. MethodsChildren (3-6 years old) were randomly assigned to 2 groups according to the diagnostic strategy used for caries detection on primary molars: VIS or RAD. Participants were diagnosed and treated according to the management plan related to the allocated group. The primary outcome was the number of new operative interventions during the 2-year follow-up period. Other secondary outcomes were also compared. Comparisons were performed with Mann-Whitney test using an intention-to-treat approach. ResultsOf the 252 children included and randomized, 216 were followed-up after 2 years (14.3% attrition rate). There was no difference between the groups for the primary outcome (P = .476). For the secondary outcomes, the RAD group had more restoration replacements (P = .038) and more restorations performed since the beginning of the study (P = .038) compared with the VIS group. In addition, the RAD group had a higher number of false-positive results than the VIS group (P < .001). ConclusionsSimultaneous use of VIS and RAD for caries diagnosis in primary molars of children who seek dental treatment does not provide additional benefits compared with VIS alone. Practical ImplicationsDentists should perform VIS only, not RAD, for detecting carious lesions in preschool-aged children.ClinicalTrials.gov: NCT02078453.

Blast from the past: Perioperative use of the Maruyama computer program for prediction of lymph node involvement in the surgical treatment of gastric cancer following neoadjuvant chemotherapy

BackgroundSurgical quality assurance is a key element of gastric cancer treatment. The Maruyama Computer Program (MCP) allows to predict lymph node involvement in stations no. 1–16. The aim of the current study was to evaluate the accuracy of the MCP predictions in GC patients treated with neoadjuvant chemotherapy (nCTH) followed by gastrectomy with adequate lymphadenectomy. Methods101 patients who underwent preoperative nCTH followed by D2 gastrectomy with curative intent were analysed. The response to nCTH was measured using the tumour regression grade system. ResultsTest sensitivity, specificity, PPV, NPV and accuracy of the MCP were 92%, 33%, 41%, 89%, and 53%, respectively. In patients with response to nCTH, number of false positive (FP) results was significantly higher than in patients who did not respond to nCTH both in the N1 (56.3% vs 28.9%, p < 0.0001) and in the N2 (59% vs 41%, p < 0.0001) trier. The risk for FP results was 6 times higher in N1 (OR = 6.50, 95%CI: 3.91–10.82,; p < 0.0001) and N2 (OR = 5.84, 95%CI: 2.85–11.96; p < 0.0001) triers. In patients with intestinal type GC, the risk for FP results was 4 times higher than in other histologic types of GC in both N1 (OR = 4.23, 95%CI: 2.58–6.95; p < 0.0001) and N2 (OR = 4.23, 95%CI: 2.02–9.62; p = 0.0002) triers. ConclusionsMCP predictions in the GC patients treated with nCTH have low specificity due to significantly high number of FP results. Noticeably low accuracy level of predictions indicate a need for new prediction models, based on Laurén classification, since it may provide some information on expected regression grade.

Interim PET-Based Outcome Prediction in Diffuse Large B-Cell Lymphoma Patients Participating in the Positron Emission Tomography-Guided Therapy of Aggressive Non-Hodgkin Lymphomas (PETAL) Trial: Comparison of the Delta SUV Max Method and the Deauville 5-Point Scale

Introduction: The recently published randomized PETAL trial (JCO 36:2024, 2018) aimed at improving outcome of aggressive non-Hodgkin lymphomas by changing therapy based on the response to the first 2 cycles of standard (R-)CHOP as assessed by interim PET (iPET). Outcome remained unaffected by treatment changes, which provided an opportunity to use the study to define the prognostic value of iPET. This report details the iPET results in the subgroup of patients (pts.) with diffuse large B-cell lymphoma (DLBCL), by comparing the deltaSUVmax method (J Nucl Med 48:1626, 2007) used in the course of the trial, with the Deauville 5-point scale (DS) which has been recommended for iPET-based outcome prediction in DLBCL (JCO 32:3048, 2014). With deltaSUVmax, a positive iPET indicating insufficient treatment response is defined as a reduction of the maximum standardized uptake value (SUV) by <66% compared to baseline. With DS, a positive iPET is variably defined as unphysiological residual activity above that of the mediastinal blood pool (DS >2) or the liver (DS >3) on the same interim scan.Methods: iPET scans for a post-hoc investigation using the Deauville criteria were available from 597 of 609 DLBCL pts. treated in the PETAL trial. For the binary cut-off variables of deltaSUVmax and DS, concordance and Spearman correlation were calculated and hazard ratios (HR) regarding event-free (EFS), overall (OS), progression-free survival (PFS), and time to progression (TTP) were determined by Cox regression. Time-dependent receiver operating characteristic (ROC) analysis (Biometrics 56:337-44, 2000) for the raw values of deltaSUVmax and DS yielded area under the curve (AUC), sensitivity, specificity, and predictive values that were accompanied with median and 95% confidence intervals (CI) obtained from a simple bootstrap with 1,000 repetitions. The integrated Brier score was used as a measure of model calibration.Results: The numbers of DLBCL pts. with a positive iPET scan were 62 for deltaSUVmax, 408 for DS >2, and 278 for DS >3. Concordance between a positive iPET according to deltaSUVmax and the DS cut-offs was 40.4% and 60.1%, and Spearman correlation was 0.17 and 0.24, respectively. HRs for a positive iPET according to deltaSUVmax were higher than for the two DS cut-offs in any time-to-event endpoint: 3.13 [CI: 2.22 - 4.46] in EFS as compared to 1.36 [0.99 - 1.85] for DS >2 and 1.38 [1.05 - 1.81] for DS >3; 3.48 [2.29 - 5.27] in OS versus 1.56 [1.03 - 2.36] and 1.91 [1.33 - 2.73]; 3.06 [2.11 - 4.43] in PFS compared to 1.22 [0.88 - 1.69] and 1.34 [1.00 - 1.80]; and 3.04 [1.97 - 4.67] versus 1.28 [0.88 - 1.88] and 1.46 [1.04 - 2.07] in TTP. ROC analysis confirmed this tendency as AUCs were higher for deltaSUVmax than for DS in all four endpoints (Table 1). Also, the difference of predictive values of the two markers favored deltaSUVmax over DS >3 in EFS (Figure 1). Similar results were obtained in the remaining endpoints and for DS >2. Calibration assessed by the Brier score was slightly better for deltaSUVmax than for DS in EFS, PFS, and TTP, and was equal in OS. Of note, when investigating the survival curves in subgroups defined by both deltaSUVmax and DS >3, pts. with negative deltaSUVmax but positive DS showed similar survival as pts. with deltaSUVmax and DS both negative, presumably indicating DS false-positives (Figure 2). The same was true for deltaSUVmax positive/DS negative pts. whose unfavorable survival curve resembled that of double-positive pts..Conclusion: DeltaSUVmax seems to be a more potent prognostic factor than DS in terms of discrimination and calibration with respect to EFS, OS, PFS, and TTP. Superior performance was shown for raw values as well as for dichotomized variables. The DS appeared unreliable due to a high number of false-positive results. Although the AUCs for deltaSUVmax were relatively low, it still seems to be a good prognostic tool with regard to HRs. Given its high positive predictive value, it may be a suitable tool to select poor-prognosis pts. in first-line for treatment approaches that have so far been reserved for later lines of therapy. [Display omitted] DisclosuresHüttmann:Roche: Other: Travel expenses; Celgene: Other: Travel expenses. Duehrsen:Amgen: Research Funding; Gilead: Consultancy, Honoraria; Roche: Honoraria, Research Funding; Janssen: Honoraria; Celgene: Honoraria, Research Funding; AbbVie: Consultancy, Honoraria.

Evaluation of the Architect HIV Ag/Ab Combo Assay in a low-prevalence setting: The role of samples with a low S/CO ratio

BackgroundThe Architect HIV Ag/Ab Combo Assay, a fourth-generation ELISA, has proven to be highly reliable for the diagnosis of HIV infection. However, its high sensitivity may lead to false-positive results. ObjectivesTo evaluate the diagnostic performance of Architect in a low-prevalence population and to assess the role of the sample-to-cutoff ratio (S/CO) in reducing the frequency of false-positive results. Study designWe conducted a retrospective study of samples analyzed by Architect between January 2015 and June 2017. Positive samples were confirmed by immunoblot (RIBA) or nucleic acid amplification tests (NAATs).Different S/CO thresholds (1, 2.5, 10, 25, and 100) were analyzed to determine sensitivity, specificity, and negative and positive predictive values (NPV, PPV). ROC analysis was used to determine the optimal S/CO. ResultsA total of 69,471 samples were analyzed. 709 (1.02%) were positive by Architect. Of these, 63 (8.89%) were false-positive results. Most of them (93.65%) were in samples with S/CO < 100. However, most confirmations by NAATs (12 out of 19 cases) were also recorded for these samples. The optimal S/CO was 2.5, which provided the highest area under the ROC curve (0.9998) and no false-negative results. With this S/CO, sensitivity and specificity were 100.0%, and PPV and NPV were 95.8% and 100.0%, respectively. In addition, the frequency of false-positive results decreased significantly to 4.15%. ConclusionsAlthough Architect generates a relatively high number of false-positive results, raising the S/CO limit too much to increase specificity can lead to false-negative results, especially in newly infected individuals.

Comparative evaluation of two diagnostic methods for the detection of chlamydia trachomatis in endocervical specimens

Context: Genital infections caused by Chlamydia trachomatis have been a significant healthcare problem recognized throughout the world in recent years. The World Health Organization estimates that approximately two million new cases of genital chlamydial infection occur annually in females. Objectives: The objective was to compare the performance of the glycogen assay test to the polymerase chain reaction (PCR) in the diagnosis of genital chlamydial infection. Materials and Methods: Consenting female patients were consecutively recruited for the study until the sample size of 365 was achieved. Two endocervical specimens were collected from each of the patients using sterile plastic-shaft Dacron swabs. C. trachomatis test kit (Autobio Company China) was used according to the manufacturer's instructions. The test is a biochemical assay for the detection of C. trachomatis in clinical samples taken from the genital tract. PCR was also done for each sample. Data management was done using the Statistical Package for the Social Sciences version 20.0. Results: Of the women studied, 95 (26%) were positive and 270 (74%) negative for genital chlamydial infection using the PCR, while 244 (66.8%) tested positive and 121 (31.2%) tested negative using the glycogen assay. Conclusions: With the results generated above and using the PCR as the standard, sensitivity for the glycogen assay was 86.3%, specificity was 40%, and the predictive value for a positive result was 33.6%, while that for a negative result was 89.3%. The glycogen assay kit is locally available, not expensive (compared to the very high cost of PCR) and often used in the diagnosis of genital chlamydial infection. However, with a sensitivity of 86.3% and specificity of 40% for the glycogen assay, found in this study, the test kit is far from ideal as a tool for the rapid diagnosis of genital C. trachomatis infection, as it will yield high numbers of false-positive results.

Evaluation of the diagnostic efficacy and spectrum of autofluorescence of benign, dysplastic and malignant lesions of the oral cavity using VELscope

ObjectivesConventional oral examination and biopsy are the only reliable methods for the early detection of oral cancer at present. Autofluorescence examination of oral tissues using the VELscope has been suggested as an adjunctive tool for cancer detection and diagnosis. The aim of our study was to evaluate the efficacy of the VELscope in recognizing dysplastic and/or neoplastic changes in oral mucosal lesions that were identified on conventional oral examination. Materials and methodsTwo hundred patients with oral mucosal lesions were subjected to conventional oral examination followed by VELscope examination and their autofluorescence characteristics were compared with the histopathological diagnosis. The sensitivity, specificity, positive and negative predictive values of the VELscope examination was calculated. ResultsThe VELscope examination showed sensitivity and specificity values of 76% (95% CI: 54.87–90.64%) and 66.29% (95% CI: 58.76–73.24%) respectively while the positive and negative predictive values were 24.36% (95% CI: 19.22–30.36%) and 95.08% (95% CI: 90.52–97.51%) respectively. ConclusionThe VELscope examination alone cannot provide a definitive diagnosis as to the presence of dysplastic tissue change. In spite of having a reasonable sensitivity, the high number of false-positive results limits its efficiency as an adjunct. However, a high negative predictive value can serve to alleviate patient anxiety regarding suspicious mucosal lesions in a general practice setting.

A new lyophilized tachyzoite based ELISA to diagnose Besnoitia spp. infection in bovids and wild ruminants improves specificity

Recent studies have reported that routinely used whole or soluble Besnoitia besnoiti tachyzoite (TZ) extract-based ELISAs potentially give rise to a high number of false-positive results, which may compromise control and the epidemiological studies of bovine besnoitiosis. Thus, western blot (WB) has been recommended as a confirmatory test. In the present study, a new ELISA test that employs lyophilized tachyzoites for the first time (BbSALUVET ELISA 2.0) was developed and validated with cattle sera (n=606) under a worst-case scenario. False positive and false negative, soluble TZ extract-based BbSALUVET ELISA 1.0 reactors were overrepresented, and WB was used as the reference test. One commercial test (PrioCHECK Besnoitia Ab 2.0, which employs whole TZ extract) and a recently developed membrane-enriched ELISA (APure-BbELISA) were also tested. The three ELISAs showed high AUC values (>0.9). However, the best diagnostic performance corresponded to the BbSALUVET ELISA 2.0 and the APure-BbELISA [(92% sensitivity (Se) and 98% specificity (Sp)] followed by PrioCHECK Besnoitia Ab 2.0 (88% Se, 98% Sp, and 4.5% doubtful results). In addition, the BbSALUVET ELISA 2.0 was validated with wild ruminant sera, and excellent performance (96% Se, 97% Sp, and 4% doubtful results) was obtained again. A different antigenic composition of the lyophilized tachyzoites, compared with whole or soluble tachyzoite extracts, may be responsible for the improved diagnostic performance. This study proposes the use of the BbSALUVET ELISA 2.0 in cattle prior to entry to herds free of the disease and in valuable samples prior to a selective culling without the need of a confirmatory Western Blot test in positive samples due to its excellent specificity.

Anti-Neospora caninum and anti-Sarcocystis spp. specific antibodies cross-react with Besnoitia besnoiti and influence the serological diagnosis of bovine besnoitiosis

Bovine besnoitiosis control remains a challenge because the disease continues to spread and control relies solely on accurate diagnosis coupled to management measures. However, recent studies have reported that routinely used ELISAs may raise a high number of false-positive results. Herein, cross-reactions between Besnoitia besnoiti antigens and anti-Neospora caninum and/or anti-Sarcocystis spp.-specific antibodies were studied in an in house ELISA since N. caninum and Sarcocystis spp. are closely related parasites, and both infections are highly prevalent in cattle worldwide. The serum panel was composed of the following categories: sera from B. besnoiti-seronegative (n=75) and -seropositive cattle (n=66), B. besnoiti-based-ELISA false-positive reactors (n=96) together with N. caninum (n=36) and Sarcocystis spp. (n=42) -seropositive reference cattle sera. B. besnoiti tachyzoite based western blot (WB) results classified animals as seropositive or seronegative. Sera were analyzed for the detection of anti-N. caninum by WB and ELISA and anti-Sarcocystis spp.-specific antibodies by WB and IFAT. Those samples recognizing a Sarcocystis spp. 18–20kDa antigenic region and N. caninum 17–18kDa immunodominant antigen were considered to be Sarcocystis spp. and N. caninum seropositive, respectively. The category of B. besnoiti based-ELISA false-positive reactors showed the highest number of sera with specific anti-Sarcocystis spp. and anti-N. caninum antibodies (74%; 71/96), followed by the N. caninum-seropositive cattle category (52.8%; 19/36). In contrast, few B. besnoiti-seronegative and -seropositive cattle showed antibodies against Sarcocystis spp. and N. caninum (10.7%; 8/75 and 1.5%; 1/66), respectively). This study revealed that B. besnoiti false-positive ELISA results were associated not only with the presence of anti-N. caninum and anti-Sarcocystis spp. antibodies (χ2: 78.36; p<0.0001; OR: 34.6; CI: 14–88) but also with high antibody levels against them using ELISA and IFAT tests, respectively (p<0.05; t-test). These results may explain why only some animals seropositive to Sarcocystis spp. and/or N. caninum are Besnoitia false-positive reactors. Therefore, sera meeting these requirements should be included in future validations of serological tests for bovine besnoitiosis.

Formation of a carbapenemase resistance detection algorithm for use in the routine laboratory

ABSTRACTThe increasing prevalence of carbapenem non-susceptible Gram negative organisms demands prompt and accurate identification of resistance mechanisms to limit their transmission. The aim of this study is to evaluate the rapid CARB screen (Rosco Diagnostica, Denmark), the ‘KPC/MBL in P. aeruginosa/Acinetobacter Confirm Kit’ (Rosco Diagnostica), Check-MDR Carba and Check-Direct CPE kits (Check-Points, The Netherlands). The purpose of this study is the formation of a carbapenemase resistance detection algorithm that can be used in the routine laboratory. Results of the rapid CARB screen kit were improved when isolates were tested from Muller Hinton agar with a meropenem 10 μg disc instead of blood agar. The rapid CARB screen (performed in 2–3 h) demonstrated overall 98.7% sensitivity and 87.7% specificity (n=133). The KPC/MBL in P. aeruginosa/Acinetobacter Confirm Kit (which requires overnight incubation) demonstrated a high number of false-positive results giving 38.6% specificity and 100% sensitivity (n=44). The Check-MDR Carba (performed in 5 h), detecting carbapenemase presence, provides a cabapenemase-positive or -negative result demonstrated 96.7% specificity and 98.6% sensitivity (n = 132). The Check-Direct CPE (performed in 3 h), which identifies KPC, NDM/VIM or OXA-48 type carbapenemases, demonstrated 96.5% specificity and 97.1% sensitivity (n=97). The Check-Direct CPE, however, failed to detect dual carbapenemase genes present in two out of four isolates. The principal conclusion is the recommendation of the rapid CARB screen and Check-MDR Carba for incorporation into a carbapenemase detection algorithm which, when used in combination, will yield results with 97.3% sensitivity and 99.6% specificity.

The ECG of high-level junior soccer players: comparing the ESC vs the Seattle criteria

IntroductionSudden cardiac death in young athletes is a devastating event. The screening and detection of potentially life-threatening cardiac pathology by ECG is difficult due to high numbers of false-positive results,...

Antiphospholipid syndrome: a clinical and laboratorial challenge.

Antiphospholipid syndrome (APS) is an acquired autoimmune thrombophilia characterized by the presence of a heterogeneous family of antibodies that bind to plasma proteins with affinity for phospholipid surfaces. The two major protein targets of antiphospholipid antibodies are prothrombin and β2-glycoprotein I (β2GPI). APS leads to aprothrombotic state, and it is characterized by the occurrence of arterial, venous or microvascular thrombosis or recurrent fetal loss. The diagnosis of APS is based on a set of clinical criteria and the detection of lupus anticoagulant (LA), anticardiolipin antibodies (ACA) or anti-β2GPI in plasma. Although laboratory tests are essential for APS diagnosis, these tests have limitations associated with the robustness, reproducibility and standardization. The standardization of diagnostic tests for detection of APLAs has been a challenge and a variety of results have been obtained using different commercial kits and in-house techniques. An increased sensitivity of the ELISA kits for detection of ACA effectively has contributed to APS diagnosis. However, the lack of specificity associated with a high number of false-positive results is a clinical and laboratorial challenge, since such results may lead to mistaken clinical decisions, such as prescription of oral anticoagulant, leading to the risk of hemorrhaging. Furthermore, clinicians are often unfamiliar with these tests and have difficulty interpreting them, requiring interaction between clinical and laboratory professionals in order to ensure their correct interpretation.

Diagnostic performance and inter-observer concordance in lesion detection with the automated breast volume scanner (ABVS)

BackgroundAutomated whole breast ultrasound scanners of the latest generation have reached a level of comfortable application and high quality volume acquisition. Nevertheless, there is a lack of data concerning this technology. We investigated the diagnostic performance and inter-observer concordance of the Automated Breast Volume Scanner (ABVS) ACUSON S2000™ and questioned its implications in breast cancer diagnostics.MethodsWe collected 100 volume data sets and created a database containing 52 scans with no detectable lesions in conventional ultrasound (BI-RADS®-US 1), 30 scans with benign lesions (BI-RADS®-US 2) and 18 scans with breast cancer (BI-RADS®-US 5).Two independent examiners evaluated the ABVS data on a separate workstation without any prior knowledge of the patients’ histories.ResultsThe inter-rater reliability reached fair agreement (κ=0.36; 95% confidence interval (CI): 0.19-0.53). With respect to the true category, the conditional inter-rater validity coefficient was κ=0.18 (95% CI: 0.00-0.26) for the benign cases and κ=0.80 (95% CI: 0.61-1.00) for the malignant cases.Combining the assessments of examiner 1 and examiner 2, the diagnostic accuracy (AC), sensitivity (SE) and specificity (SP) for the experimental ABVS were AC = 79.0% (95% CI: 67.3-86.1), SE = 83.3% (95% CI: 57.7-95.6) and SP = 78.1% (% CI: 67.3-86.1), respectively.However, after the ABVS examination, there were a high number of requests for second-look ultrasounds in up to 48.8% of the healthy women due to assumed suspicious findings in the volume data.In an exploratory analysis, we estimated that an ABVS examination in addition to mammography alone could detect a relevant number of previously occult breast cancers (about 1 cancer in 300 screened and otherwise healthy women).ConclusionsThe ABVS is a reliable imaging method for the evaluation of the breast with high sensitivity and a fair inter-observer concordance. However, we have to overcome the problem of the high number of false-positive results. Therefore, further prospective studies in larger collectives are necessary to define standard procedures in image acquisition and interpretation. Nevertheless, we consider the ABVS as being suitable for integration into breast diagnostics as a beneficial and reliable imaging method.

Compartment Pressure Measurements Have Poor Specificity for Compartment Syndrome in the Traumatized Limb

BackgroundOsseofascial compartment syndrome is defined by ischemic necrosis of muscle caused by elevated pressure within fascial compartments. The diagnosis can be made either clinically or through compartment pressure measurements. Compartment pressure above 30 mm Hg was traditionally used as the threshold for diagnosis of compartment syndrome, but was challenged due to a high number of false-positive results. Perfusion pressure (diastolic blood pressure − compartment pressure) <30 mm Hg came to be promoted as a confirmatory diagnostic test. ObjectiveThe objective of this article is to review the specificity of perfusion pressure for compartment syndrome in the acutely traumatized limb. DiscussionPerfusion pressure has been shown to generate false-positive results in 18–84% of patients with tibial fractures. Two studies showed that not a single patient with measurements qualifying for fasciotomy actually needed the procedure. ConclusionBoth absolute compartment pressure and tissue perfusion pressure generate a high rate of false-positive results in the acutely traumatized limb. An alternative diagnostic test or process is needed to prevent overtreatment. In the meantime, emergency medicine and orthopedic surgery textbooks and guidelines should promote awareness of the limitations of the test.